"Newer models all have BT"
Right, there is only 1 "Newer" model.
Unless you include the 8th generation devices, in which case only one of those two have BT. For at total of two out of the three.

The post I quoted:

The current (7th. generation) Paperwhite does have "some sort of audio", yet no one else seems to be saying that it is anywhere other than in the "Paperwhite territory".
Or if they are, they are a couple years too late in pointing it out.

Has it been established that Oasis 1 lacks bluetooth capability? FCC paperwork tied to Oasis indicated testing for both Wifi and Bluetooth:

Moreover, the press release states that the Audiobook feature would be coming to both 8th gen devices (Kindle, and Kindle Oasis):

Quote:

Audible will be available on the all-new Kindle Oasis via a free over-the-air update when the device ships—and it will be available via a free over-the-air update to Kindle (Gen 8) and the first Kindle Oasis in the coming months.

This is strong evidence that Oasis 1 is BT-capable (just as with 8th gen Kindle) and awaits a software update to enable it. Oasis’ unique design (necessitating the need to flip the screen 180 degrees to switch hands) does not lend itself to having a wire hanging off of it for audio. Nor is there room for a speaker, given the priority given to thinness and lightness.

Oasis 1 does support VoiceView with the audio dongle used with Paperwhite (Voyage too), the first Kindle to have VoiceView. But it requires the charging cover to be attached to function. And (more than a headset wire) the dongle is a rather awkward thing to have hanging off, so there goes any pretense at ergonomics. Nobody would be happy with this just to have audio (VoiceView users can do just as well without lighted screens and page turn buttons, so the $79 Kindle or $119 Paperwhite will do just fine).

Moreover the act of plugging in the dongle turns on VoiceView. That is not really compatible with the Audible feature. Software update could change this behavior, but then we’re back to turning Oasis into this ugly thing with dongle hanging off of it. So the most plausible scenario is that the software update will enable BT on Oasis 1 for both Audiobook and VoiceView, just as with Oasis 2 and Kindle 8th gen (while disabling the support for audio dongle).

I can imagine that the Audible feature was in the works for awhile, but was not ready when 8th gen devices shipped (just as VoiceView was not ready when Paperwhite 3 shipped). Now they’re using Oasis 2 launch to reveal it (and the actual feature only arrives by update after you take it out of the box and register it).

Paperwhite 7th gen also has audio capability, as we learned some months after it shipped with the announcement of VoiceView on Kindle. It is one of the main reasons they bumped RAM up to 512MB (so voice data could be kept in RAM). But it is not getting Audible, because they would have to eliminate the dead-simple way of enabling VoiceView (by plugging the dongle in) and that would draw the ire of the AFB and others whose lawsuits brought about VoiceView in the first place.